Tamp pad

ABSTRACT

Tamp printing of at least one picture ( 4 ) occurs by means of at least one tamp pad ( 1, 18, 24, 34 ) on a piece ( 3 ), which has boundary surfaces ( 5, 13 ) forming angles relative to each other, the tamp pad first printing in one direction ( 10 ) against a boundary surface ( 13, 43 ) and thereafter, after further compression of the tamp pad ( 1 ) against said boundary surface ( 13 ) due to its deformation, prints in another direction ( 45 ) than the direction ( 10 ) against another boundary surface or other boundary surfaces ( 5, 43 ), whereby the picture is transferred to said boundary surfaces.

This application is a divisional of application Ser. No. 09/467,535,filed on Dec. 20, 1999 now U.S. Pat. No. 6,244,172. This applicationclaims priority from Swedish Patent Application No. 9804539.6, filed onDec. 21, 1998.

FIELD OF THE INVENTION

The present invention relates to a device and a method at a tamp pad andat tamp printing intended to simplify the printing method, in which inkis applied on a tamp pad, that prints a picture on a piece havingconcave sides and a convex bottom, wherein the tamp pad has a shape inconformity with the piece for printing on the bottom and sides of thepiece and can be provided with channel means for conveying away airaccumulated between the piece and the tamp pad, so that the ink can beapplied on surfaces difficult to access.

BACKGROUND OF THE INVENTION

In designs of this kind appearing on the market it is possible by meansof a method called tamp printing to transfer a picture to a piece onsurfaces which are only slightly curved, for example a ball, a frontside on a mobile telephone etc. The principle for tamp printing of metalink is described for example in PCT/SE97/00372 and PCT/SE98/01678, whichare hereby incorporated by reference. The printing with good result onsurfaces with corners and neighbouring sides and/or other formations,such as holes, recesses or elevations, is difficult with presenttechnique to tamp print, as the tamp pad will not print satisfactory incorners and as it is not designed to print on neighbouring sides andfurther as it is not capable of allowing accumulated air in the cornersto escape, as the tamp pad covers the air accumulation from alldirections, so that the ink will not be applied on the piece at theselocations. This means that great areas will not be covered by ink. Thisis a great problem, as this method has to be limited to use on piecesnot having a complicated shape as mentioned above.

At the manufacture of electronic units, for example mobile telephones,an electrically conductive layer is needed for shielding offelectromagnetic radiation which layer is provided by inks containing agreat proportion of metal fragments which conduct current. By means oftamp printing it is possible to print such a layer solely on simplesurfaces, which only has a moderately curved surface, and sides,corners, holes, smaller elevations etc can not be printed. By means ofother known methods, which are more expensive to use, such as vacuumvaporizing and spray painting, it is possible to provide these unitswith an electrically conductive layer also on places difficult toaccess. Otherwise leakage of electromagnetic radiation appears at holesin the layer.

Thus, tamp printing is a comparably very cheap method, as costs forremoving undesired ink at undesired places, for example at holes, screwconnections and front sides, can be dispensed with. There is further nospillage of ink, as only the needed picture is printed. The machinesused for this method are cheaper. It is also simple to automate themethod, which means that the labour cost also is low. For this reason itis very interesting to solve the problems with said methods, so thattamp printing in corners and their neighbouring sides as well as oncurved surfaces and irregularities becomes possible.

SUMMARY OF THE INVENTION

An object of the present invention is thus to eliminate the drawbacksinherent with the designs mentioned above by adopting the shape of thetamp pad in accordance with the design of the piece with concave andconvex surfaces, so that at least a neighbouring side of the piece canbe concurrently printed by providing the tamp pad with recessesventilating away the air accumulations at the corners and other holespaces of the piece, so that the tamp pad is no longer prevented fromprinting in the mentioned spaces, which are difficult to access.

According to the invention an adaption of the appearance and shape ofthe tamp pad after the piece to be printed has now been accomplished inthat the pad is provided with concave and convex surfaces; further theproblem has been solved with the air accumulations formed at theprinting and preventing application of ink on the surfaces difficult toaccess for the tamp pad by transferring the air away from these placesvia channels and/or hole means in the tamp pad.

According to the invention the tamp pad has at least one corner,generally formed by two sides forming an angle with each other, saidsides printing in two stages two neighbouring sides of the piece, sothat the substantially horizontal surface of the piece is first printed,when the tamp pad moves generally downwards. Stage two means that thesoft tamp pad at continued downwards movement is flattened against thebottom of the piece, so that a counterpressure is formed, which in turncauses a deformation of the tamp pad, which then expands sidewise,contacting at least an angled side of the piece, so that the tamp padthen is able to print this side. Via a channel, which runs from a cornerof the tamp pad upwards all the way to the upper part of the tamp pad,an air accumulation formed at this corner and created at depressing thetamp pad against the piece is conducted away. This means that the ink isnot prevented by the air accumulation to reach the corner and otherplaces which otherwise would be difficult to access. In a preferredembodiment of the invention the ink is first fetched from a printingblock, which is covered with the intended picture. For accomplishingthat the picture is also attached to the sides of the tamp pad, theprinting block has a shape adapted to the shape of the tamp pad when theink is fetched. The tamp pad can also move pivotally over the printingblock, wherein the side is first applied against the printing block, sothat it is provided with ink. Thereafter the pivotal movement of thetamp pad is continued with continued contact with the printing block, sothat the contact angle with this is continuously changed, the remainderof the picture thereby being attached to the tamp pad. The ink can alsobe fetched from a rotating printing block, that emits the ink to arotating tamp pad. Combinations of a curved printing block and amovement of the tamp pad can of course also be possible for transferringthe entire picture to the tamp pad. At the tamp printing of a piecewhich is formed as the inside of a mobile telephone cover the tamp padaccording to the invention in its preferred embodiment is formedgenerally as a block provided with a convexly curved underside.Connecting thereto in the hereby formed corners are four generallyvertically connecting, concavely curved sides. The upper side of theblock does not contact the piece at printing, which means that it canhave any shape. When the ink, which constitutes a picture, now shall beprinted on the piece, this is accomplished in three stages. First thepicture is transferred to the horizontal part of the piece, for examplea cover of a mobile telephone, when the bottom of the block is appliedon this place. A continued compression of the tamp pad in stage twodeforms the convex bottom surface, this deformation being transferredthrough the tamp pad, so that the convex sides come in contact with thegenerally vertical sides of the piece, which means that also these aretamp printed. The marked corners of the tamp pad will according to theinvention be pressed into the corners of the piece in stage three. Inthe irregularities of a piece it may be difficult to access with a tamppad with printing ink. This is according to the invention solved byshaping the tamp pad as exactly as possible after the piece to beprinted. For this reason the tamp pad is provided with projectionscorresponding to recesses in the piece and recesses in the tamp padcorresponding to projections of the piece. Hole means and projections ofthe tamp pad can also need to be aired via aeration channels in order toremove the air accumulations which prevent the ink from adhering to thepiece in accordance with the description above. It is also possibleaccording to the invention to form the tamp pad as a rotating wheel,which fetches its picture via a rotating wheel shaped printing block,which is continuously provided with ink, so that the rotating tamp padcan emit its picture to a piece moving at the same speed as the rotatingtamp pad.

As in the above described method to tamp print in three stages, also therotating tamp pad can do the same; the tamp pad is provided with aconvex bottom and concave sides and is compressed, so that the sides canprint on the sides of the piece. Likewise, the rotating tamp pad can beprovided with projections and recesses for enabling printing on leastaccessible places on the piece. It can also be provided with aerationchannels for ventilating away air accumulations described above. By themethod of a form adapted tamp pad provided with recesses it will becomepossible to tamp print on parts of and/or entire pieces equipped withcomplicated details, such as corners, hole means and projections. Incomparison with other methods, the most important advantages with theinvention is that the method is much cheaper and faster and gives aresult which is improved in form of entirely covered surfaces even oncomplicated parts of the piece with a reduced number of tamp printings.With this method the piece does not need to be tamp printed severaltimes from several directions for covering all surfaces of the piece.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described by means of some preferredembodiments under reference to the enclosed drawings, in which

FIG. 1 is a section through a tamp pad according to the presentinvention in the first stage of a printing method, before it prints onthe bottom of a piece,

FIG. 2 is a section of the same tamp pad according to the presentinvention in the second stage of a printing method, when it prints onthe bottom of a piece,

FIG. 3 is a section of the same tamp pad according to the presentinvention in the third stage of a printing method, when it prints on thesides of a piece,

FIG. 4 is a section through an alternative embodiment of a tamp padaccording to the present invention, before it prints on a piece,

FIG. 5 is a schematic perspective view of a tamp pad according to theinvention, provided with aeration channels, and

FIG. 6 is a view of a rotating tamp pad, which is provided with tamp padportions, and a section through an associated conveyor belt with pieces.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

A first stage in a tamp printing method is shown in FIG. 1, the deviceaccording to the invention having a first embodiment of a tamp pad 1,which is formed of a soft material, preferably silicon, and which ismoving generally in a direction 10. The pad is attached to an attachmentdevice 2 of a tamp printing machine, a picture 4, which preferablyconsists of one colour containing metal fragments for being electricallyconductive, being fetched from a printing block, whereafter it shall beprinted on a piece 3, for example on an inside 5 of a mobile telephonecover 11. The tamp pad 1 has a number of external boundary surfaces 26,at least one such surface being a side 7, which has a convex form, andneighbouring boundary surfaces, which form corners 8, and at least twoconcave sides 9. The piece 3 has at its inside 5 corners 12, a bottom 13and at least two sides 14.

A second stage of the tamp printing method is shown in FIG. 2. When theside 7 of the tamp pad 1 has approached the bottom 13 of the piece 3 andhereby started to cover the majority hereof, a portion of the picture 4commences to adhere to the inside 5 of the piece 3. At the commencementof the deformation the side 7 of the tamp pad 1 is flattened out, sothat its previously concave sides 9 are straightened out in anintroductory phase of stage two, until they are getting slightly convexat the end of stage two. Hereby the corners 8 of the tamp pad approachthe corners 12 of the piece.

A third stage of the tamp printing method is shown in FIG. 3. In thisposition the tamp pad 1 has reached its maximum bottom position, whereinit has covered the entire inside 5 of the piece 3 with its entire side 7and associated corners 8 and sides 9, the entire picture 4 now havingbeen attached to the inside 5 of the piece 3. It is of course possiblefor the tamp pad 1 to move in a direction 45. Then the side 9 is madeconvex and the side 7 concave, so that the side 14 is first tampprinted, the deformation of the tamp pad deforming the concave side 7,so that it becomes convex and tamp prints the bottom 13 of the piece 3.In order that an air accumulation 15 at the corner 8, 12 shall notprevent the picture 4 from attaching here, it is emptied via aerationchannels 16, which may be designed as through channels in the tamp pad 1and/or as recesses in the form of for example grooves somewhere in thesurface of the tamp pad 1, such grooves extending from the airaccumulation 15 to upper parts 17 of the tamp pad 1 free from the piece3, so that the air is not prevented by the piece 3 from escaping.

A second embodiment of a tamp pad 18 is shown in FIG. 4. This pad 18 isprovided with at least a number of concave sides 19 and a number ofconvex sides 20 and is shown in stage one according to FIG. 1. Accordingto the invention it is possible to tamp print on a substrate with morethan one bottom 13 and more than two sides 14 in the same processgenerally in one direction 10. Then also convex corners can be tampprinted. Also in this embodiment all corners may need to be airedthrough aeration channels 23, as has been described above. The picture 4is transferred in accordance with the three stages as has been describedabove to the inside of the piece 21.

A tamp pad 24 is shown in perspective in FIG. 5. This pad 24 showexamples of different types of aeration channels 25, which have thepurpose of ventilating away the air accumulations 15 mentioned inrelation to FIG. 3 above. These channels can be designed as aerationchannels 25 arranged in the outer boundary surface 26 of the tamp pad 24in accordance with enlargement A. They may also be designed as aerationholes 27, which run from the outer boundary surface 26 at the corner 8and then open on the upper side of the tamp pad 24 in accordance withenlargement B. The aeration channels 25 may also wholly or partly runinside the tamp pad 24, as is shown in enlargements B and C.

FIGS. 1-3 illustrate the three separate stages in a printing method.These stages are also performed in a tamp printing method describedbelow, wherein a rotating tamp pad 1 according to FIG. 6 is like a tyre28 in a side view, and its attachment device 2 is like a hub 29 in awheel rotating in direction 31 around a shaft 30. The upper side 17 ofthe tamp pad 1 is then closest to the shaft 30. In this tamp printingmethod the piece 3, which is shown in section, is transferred on aconveyor belt 32 with the same speed and direction as the rotation ofthe tamp pad 1. The pad 1 is provided with notches 33, which means thatthe tamp pad 1 is divided into several tamp pad portions 34, whichindividually may tamp print the inside 5 of a piece 3 with a picture 4.Printing ink is also applied in a continuous process from an inkcontainer 41 on the tamp pad portions 34 of a rotating printing block40, which can be made so small that it can be housed in the notches 33,and thus it becomes possible to transfer the picture on its boundarysurfaces 26. A further rotating printing block can of course be arrangedat at least one of the sides 44 of the rotating tamp pad portion 34, sothat it further can tamp print on the inside 43 of the piece 3. Underits continuous rotation the tamp pad 1 applies a constant pressureagainst the piece 3. In stage one the tamp pad portion 34 being in aposition 35 is on its way in the direction towards the piece 3. In stagetwo it is in a position 36, wherein the bottom 13 is in the commencingphase of the tamp printing, and in stage three in a position 37 also theinside 14 is tamp printed. These three stages are similar to the stagesdescribed above with reference to FIGS. 1-3, the tamp pad portions 34being provided with concave and convex sides. The tamp pad portions 34have tamp printed the piece 3 in a position 38, when the piece 3 is inposition 39. In position 42 the piece 3 is not yet tamp printed but isnext to be printed. The tamp pads 34 can of course be designed and beventilated in different ways for adapting to the piece to be tampprinted, as appears from FIGS. 4 and 5. It appears that the piece 3described above is a mobile telephone cover, the tamp pad portions 34 onthe rotating tamp pad 1 printing metal layers on covers passing byaccording to the assembly line principle, as appears from FIG. 6.

The tamp printing method described above can of course be used forprinting parts of pieces 3 both externally and/or internally with anumber of non-rotating tamp pads and/or tamp pad portions rotating inthe same tamp printing machine, each tamp pad constituting a sub-stationin the tamp printing method. This can be performed while the piece isstationary and/or moving.

The description above is only of preferred embodiments of the invention,and the scope of the invention is only defined by the appended claims.

1. A method of tamp printing using at least one tamp pad having at leasta convex side and a concave side on a piece having a plurality ofboundary surfaces forming angles in relation to one another, the methodcomprising the steps of: compressing the at least one tamp pad against afirst boundary surface; causing the convex side of the at least one tamppad to deform by the compression, the deformation of the convex sidecausing printing of at least one picture in a first direction againstthe first boundary surface of the plurality of boundary surfaces; andcausing at least a portion of the concave side of the at least one tamppad to deform by the compression into a non-concave shape, and printingtherefrom of at least one picture in a second direction against a secondboundary surface of the plurality of boundary surfaces.
 2. The methodaccording to claim 1, wherein said piece comprises a mobile telephonecover and said plurality of boundary surfaces comprise inside surfacesof said mobile telephone cover.
 3. The method according to claim 2,wherein said at least one picture comprises an electrically conductivelayer.
 4. The method according to claim 1, wherein the at least one tamppad comprises a rotating tamp pad rotating around a shaft.
 5. The methodaccording to claim 4, wherein said rotating tamp pad comprises at leastone intermediate notch dividing the rotating tamp pad into a pluralityof tamp pad portions, the plurality of tamp pad portions each being ableto individually print said at least one picture against an insidesurface of the piece.
 6. The method according to claim 5, wherein thesteps of printing in said first and second direction further comprise:applying ink from an ink container to at least one rotating printingblock responsive to rotation of the at least one tamp pad, said at leastone rotating printing block being in rotating contact with the at leastone tamp pad, thereby transferring the at least one picture to theplurality of tamp pad portions; and transferring said at least onepicture from the plurality of tamp pad portions to a plurality ofpieces.
 7. The method according to claim 6, wherein said plurality oftamp pad portions of said rotating tamp pad prints said at least onepicture on an inside surface of the plurality of pieces, wherein theplurality of pieces pass said rotating tamp pad on a conveyor belt. 8.The method according to claim 1, wherein said at least one picturecomprises an electrically conductive layer.
 9. The method according toclaim 2, wherein the at least one tamp pad comprises a rotating tamp padrotating around a shaft.
 10. The method according to claim 3, whereinthe at least one tamp pad comprises a rotating tamp pad rotating arounda shaft.
 11. The method according to claim 8, wherein the at least onetamp pad comprises a rotating tamp pad rotating around a shaft.
 12. Themethod according to claim 9, wherein said rotating tamp pad comprises atleast one intermediate notch dividing the rotating tamp pad into aplurality of tamp pad portions, the plurality of tamp pad portions eachbeing able to individually print said at least one picture against aninside surface of the piece.
 13. The method according to claim 10,wherein said rotating tamp pad comprises at least one intermediate notchdividing the rotating tamp pad into a plurality of tamp pad portions,the plurality of tamp pad portions each being able to individually printsaid at least one picture against the inside surfaces of the mobiletelephone cover.
 14. The method according to claim 11, wherein saidrotating tamp pad comprises at least one intermediate notch dividing therotating tamp pad into a plurality of tamp pad portions, the pluralityof tamp pad portions each being able to individually print said at leastone picture against an inside surface of the piece.
 15. The methodaccording to claim 12, wherein the steps of printing in said first andsecond direction further comprise: applying ink from an ink container toat least one rotating printing block responsive to rotation of the atleast one tamp pad, said at least one rotating printing block being inrotating contact with the at least one tamp pad, thereby transferringthe at least one picture to the plurality of tamp pad portions; andtransferring said at least one picture from the plurality of tamp padportions to a plurality of pieces.
 16. The method according to claim 13,wherein the steps of printing in a first and second direction furthercomprise: applying ink from an ink container to at least one rotatingprinting block responsive to rotation of the at least one tamp pad, saidat least one rotating printing block being in rotating contact with theat least one tamp pad, thereby transferring the at least one picture tothe plurality of tamp pad portions; and transferring said at least onepicture from the plurality of tamp pad portions to a plurality ofpieces.
 17. The method according to claim 14, wherein the steps ofprinting in a first and second direction further comprise: applying inkfrom an ink container to at least one rotating printing block responsiveto rotation of the at least one tamp pad, said at least one rotatingprinting block being in rotating contact with the at least one tamp pad,thereby transferring the at least one picture to the plurality of tamppad portions; and transferring said at least one picture from theplurality of tamp pad portions to a plurality of pieces.
 18. The methodaccording to claim 16, wherein said plurality of tamp pad portions ofsaid rotating tamp pad print said at least one picture on an insidesurface of the plurality of pieces, wherein the plurality of pieces passsaid rotating tamp pad on a conveyor belt.
 19. The method according toclaim 16, wherein said plurality of tamp pad portions of said rotatingtamp pad print said at least one picture on an inside surface of theplurality of pieces, wherein the plurality of pieces pass said rotatingtamp pad on a conveyor belt.
 20. The method according to claim 16,wherein said plurality of tamp pad portions of said rotating tamp padprint said at least one picture on an inside surface of the plurality ofpieces, wherein the plurality of pieces pass said rotating tamp pad on aconveyor belt.